In recent years, materials particularly for forming a color image are predominating as the image recording material. More specifically, a recording material using an inkjet system, a recording material using an electro-photographic system, a silver halide light-sensitive material using a transfer system, a printing ink, a recording pen and the like are popularly used.
In these color image recording materials, three primary color dyes (dyes or pigments) by a so-called additive or subtractive color mixing method are used for reproducing or recording a full color image, however, a dye having absorption properties capable of realizing a preferred color reproduction region and having fastness capable of enduring various use conditions is not found at present and improvements are keenly demanded.
The inkjet recording method is abruptly overspread and still making a progress, because the material cost is low, high-speed recording can be performed, noises are less generated at the recording and color recording is facilitated.
The inkjet recording method includes a continuous system of continuously jetting out a liquid droplet and an on-demand system of jetting out a liquid droplet according to image information signals, and the ejection system therefor includes a system of ejecting a liquid droplet by applying a pressure using a piezoelectric element, a system of ejecting a liquid droplet by generating a bubble in the ink using heat, a system of using an ultrasonic wave, and a system of ejecting a liquid droplet by suction using an electrostatic force. With respect to the inkjet recording ink, an aqueous ink, an oily ink or a solid (fusion-type) ink is used.
The dye used in such an inkjet recording ink is required to exhibit good solubility or dispersibility in a solvent, enable high-density recording, provide good color, be fast to light, heat and active gases in the environment (for example, oxidative gases (e.g., NOx, ozone) and SOx) and highly resistant against water and chemicals, ensure good fixing and less blurring on an image-receiving material, give an ink having excellent storability, have high purity and no toxicity and be available at a low cost. However, it is very difficult to find out a dye satisfying these requirements in a high level. In particular, a dye having good black color hue and being fast to light, humidity and heat, especially at the printing on an image-receiving material having an ink-accepting layer containing a porous inorganic white pigment particle, being fast to oxidative gases in the environment, such as ozone, is strongly demanded.
In color copiers and color laser printers utilizing an electrophotographic system, a toner generally obtained by dispersing a coloring material in a resin particle is widely used. The performance required of the color toner includes absorption property capable of realizing a preferred color reproduction region, particularly high transmittance (transparency) which is required upon use with an over head projector (hereinafter referred to as “OHP”), and various fastnesses in the environmental condition on use. The toner is generally obtained by dispersing a pigment as the coloring material in a particle. The toner using a pigment exhibits excellent fastness, however, the color reproducibility is inferior to that of a toner using a dye and since the toner is insoluble, aggregation readily occurs to give rise to reduction in the transparency or change in the color hue of transmitted color. On the other hand, a toner using a dye as the coloring material is disclosed in JP-A-8-123085 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). The toner using a dye disclosed in these patent publications is high in the transparency and free from change in the color hue but generally has a problem in the light fastness.
The dyes used for various uses described above are commonly required to have the following properties. That is, the dye has, for example, absorption characteristics preferred in view of color reproduction, has good fastness in the environmental condition on use, for example, light fastness, heat resistance, humidity resistance, resistance against oxidative gases such as ozone, and resistance against chemicals such as sulfurous acid gas, and has a large molar absorption coefficient.
Heretofore, disazo dyes and trisazo dyes have been generally used as the black dye. For the raw material of these disazo and trisazo dyes, non-heterocyclic compounds such as phenol, naphthol, naphthylamine and aniline are being widely used. As for the disazo dye obtained from such raw materials, the dyes disclosed, for example, in European Patent No. 0761771 are known, however, these dyes all are poor in the light fastness and furthermore, the fastness to oxidative gases such as ozone is extremely insufficient.
After studies to develop a coloring agent fast to oxidative gases such as ozone, the present inventors have reached a thinking of using mainly a heterocyclic compound as the raw material by departing from use of conventional raw materials such as phenol, naphthol, naphthylamine and aniline. A water-insoluble disazo or trisazo dye containing two or more heterocyclic rings is described, for example, in German Patent No. 2743097 and JP-A-59-133259. However, the dyes described all are a so-called disperse dye or reactive dye and developed for the dyeing of fiber. These patent publications are absolutely silent on the performances required in the present invention, that is, whether or not the dye has absorption characteristics preferred in view of color reproduction and the dye has fastness in the environmental condition on use (for example, light fastness, heat resistance, humidity resistance, resistance against oxidative gases such as ozone, which is particularly required in the inkjet image formation, and resistance against chemicals such as sulfurous acid gas) Moreover, it is completely unknown what structure is optimal for the image formation of the present invention.